1. Field of the Invention
This invention relates to detection circuits and, more particularly, to undervoltage detection circuits and undervoltage lockout circuits.
2. Description of the Related Art
Many circuits are sensitive to fluctuations in supply voltage. More particularly, when the supply voltage decrease below a minimum specified operating voltage, an undervoltage condition may occur. Some circuits may either be damaged or they may exhibit unpredictable operation when operated in an undervoltage condition. The unpredictable operation may be especially critical in circuits that include processing engines such as microprocessors, microcontrollers, and digital signal processors, for example.
Depending on the type of system, there may be various reasons for undervoltage events. In a typical battery-operated system such as a portable communication or computing device, for example, the charge (and thus the voltage potential) stored in the battery will inevitably decay. To prevent damage or unpredictable circuit operation, it may be desirable to disable circuit operation during undervoltage events.
Some systems may employ an undervoltage detection/lockout circuit to prevent operation of system circuits during undervoltage conditions. In such systems, the detection/lockout circuit may enable the system circuits to operate while the battery voltage is above a predetermined threshold voltage and may disable the system circuits when the battery voltage drops below the threshold voltage. Some conventional undervoltage detection/lockout circuits employ a bandgap circuit for generating a temperature independent reference voltage and a separate comparator circuit for comparing the bandgap reference voltage to a voltage divided representation of the battery voltage. Unfortunately, these conventional implementations of undervoltage lockout circuits may utilize a relatively large amount of circuitry (e.g., and thus circuit area) and/or may consume a relatively large amount of power during operation.